Phosphors are used in fluorescent tubes, fluorescent display tubes, luminous display panels and other applications, and those usages are expanding. Additional recent trends include attempts to combine the phosphor with LED for use in various display devices such as a TV monitor as well as an advance in the research and development relating to white phosphor, which holds promises for a wide range of use.
Turning to fluorescent materials including those of natural substances, they exist in various organic and inorganic forms, and research and development efforts are made by working with different materials to improve a desired luminescent color, spectral intensity at peak emission, and economic efficiency. Specifically, research and development efforts are made in relation to SiALON based phosphor and aluminum oxide based phosphor.
Concerning the SiALON based phosphor, Patent Document 1 discloses a β-SiALON phosphor comprising a luminescence center element including Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm or Yb.
Concerning the aluminum oxide based phosphor, Patent Document 2 discloses a green phosphor having a β-alumina structure, wherein the composition of the fluorescent layer is represented by the general formula A(Zn1−x−yMgxMny)Al10O17 (wherein A is an element selected from Ca, Ba and Sr, x is a number satisfying 0.01≦x≦0.3, and y is a number satisfying 0.02≦x≦0.14).
Patent Document 3 discloses an alkaline-earth aluminate based phosphor which is at least partially crystallized in a β-alumina form. More specifically, it discloses a compound phosphor having a composition corresponding to the following formula: a(M1O).b(MgO).c(Al2O3) (1) (wherein, M1 denotes at least one of alkaline-earth metal elements, a, b and c are independently an integer or non-integer satisfying the relationship of 0.25≦a≦4; 0≦b≦2 and 0.5≦c≦9), wherein M1 is partially substituted by europium and at least one other element selected from rare earth elements having an ionic radius smaller than that of Eu3+, and wherein the compound is substantially in the form of a full particle with an average size of 6 μm or less.